This invention relates to a process for the removal of calcium from petroleum crudes and heavy hydrocarbonaceous residua using acetic acid in an aqueous solution having a pH in a particular pH range. A number of important crude feedstocks, or the residua or deasphalted oils derived from them, contain levels of calcium which render them difficult to process using conventional refining techniques. The calcium which causes particular problems is present in these feedstocks as organically-bound compounds, which are not easily dissociated or removed by conventional water washing or desalting processes. These calcium compounds quickly decompose during typical catalytic operations, such as during hydroprocessing or during fluid catalytic cracking, causing rapid fouling or deactivation of the catalysts in the catalytic operation. It is desirable to remove these compounds before additional processing.
In U.S. Pat. Nos. 4,778,589; 4,778,590; 4,778,591; 4,778,592; 4,789,463; 4,853,109; 5,593,573 and 4,988,433, commonly assigned to the assignee of the present invention, various agents including mineral acids, aminocarboxylic acids, hydroxo-carboxylic acids, dibasic carboxylic acids, monobasic carboxylic acids and carbonic acid, and their salts, are generally taught for removing organically-bound calcium from hydrocarbonaceous feedstocks.
In Lerner U.S. Pat. No. 3,052,627, metal contaminants are removed from crude petroleum feedstocks using a 2-pyrrolidone-alcohol mixture. In Payne U.S. Pat. No. 3,167,500, metallic contaminants, such as metal-containing porphyrins, are removed from petroleum oils using a condensed polynuclear aromatic compound having a preferred C/H ratio and molecular weight. In Eldib et al., U.S. Pat. No. 3,153,623, selected commercially available organic compounds of high dielectric strength were added to assist in a process basically encompassing the electrically-directed precipitation of metals. Duke U.S. Pat. No. 4,439,345, discloses the use of carboxylic acids to demulsify by demetalizing the middle phase emulsion of an enhanced oil recovery product. Krambeck, et. al. U.S. Pat. No. 4,645,589, discloses a method for removing vanadium and nickel metal porphyrins from hydrocarbon oils using phosphoric acid and its salts. Powell U.S. Pat. No. 2,778,777, teaches the use of relatively high concentrations of sulfuric acid for the removal of porphyrinic heavy metals, such as vanadium, nickel and iron. Powell also teaches the removal of inorganic metal salts of light metals, such as calcium, sodium, and magnesium, also using relatively high concentrations of sulfuric acid, and ordinary desalting technology.
Japanese Patent Publication Sho No. 5230284, Fushimi, teaches a method for removing various metal contaminants from crude oil using a combination of mineral acid, alkyl phosphate ester and an oxidant. Japanese Patent Publication Sho No. 4722947 teaches a lower level of metals removal using a combination of alkyl phosphate esters and alkyl carboxylic acid in the presence of mineral acids.
Norman U.S. Pat. No. 4,432,865, teaches a process for treating used motor oil to remove metals using a polyhydroxy compound and a polyfunctional mineral acid.
However, a need remains for cheaper and more efficient methods for removing calcium from petroleum oils.